`adb install` was writing success to stderr rather than stdout.
Server mismatch messages were going to stdout rather than stderr.
Error messages should consistently start with a lower case letter.
Also improve consistency of syntax error reporting.
Bug: https://issuetracker.google.com/37128706 (adb install success to stdout)
Bug: https://issuetracker.google.com/37140458 (server mismatch on stderr)
Bug: http://b/32413861 (consistency)
Test: ran tests
Change-Id: I0d6cb0c7482bec03483dacefd996644b7a28d273
bugreport() will be soon refactored to track progress, which will
require more comprehensive unit tests.
As such, it's better to move it to its own files, which in turn also
requires moving send_shell_command() and usage() to commandline.h.
Fixes: 30100363
Bug: 30268737
Change-Id: I3cdf114a0b5547293320042ff0749a60886440b0